In With the Old ...

02/23/2006 | By Jim Widmer

The New Year traditionally brings a sense of housecleaning and starting fresh. But, just like that comfortable pair of jeans in the back of your closet, some things stand the test of time - even if your spouse doesn’t agree!

That aside, thus far it’s been a very mild winter in the Northeast, with more days in the 40s and 50s than below freezing, and as of this writing, we have had no snow on the ground in my hometown of Syracuse, NY. Though we’ve had about 65 inches of total snow accumulation since November, it’s been washed away by heavy rains. Global warming or just a fluke?  After so many harsh winters in a row, maybe we’re just due for a mild one. Of course, we still have a good 6 to 8 weeks of winter ahead of us, so I guess I shouldn’t put the shovel away just yet. But, it does bring to mind a few thoughts. 

Like most of you have experienced, in early December, the utility in my area dramatically increased rates for home heating in response to the rising cost of oil, Hurricane Katrina’s impact, and the anticipation of more oil-price increases coupled with supply issues. I got hit with a 35-percent increase, and that was just based on estimates - not my actual usage. Then they said to expect more increases per kW as winter progressed. Thank goodness it’s been mild and we’ve been able to set back the thermostat a few degrees below our normal comfort setting for this time of year! But, we pay for this more than once. There’s the impact on the family budget, and then there’s the impact on the cost of goods and services, as businesses need to pass along their higher costs to customers. Now, think about the really big energy consumers - shopping malls, office buildings, factories, hotels, and hospitals. That’s when the moment of crystallization should take place, when we realize what should have been done long ago to protect ourselves against the fluctuations of the volatile oil market.

Take, for example, the application of Dedicated Heat Recovery Chillers (DHRCs). Ben Kincaid of Indianapolis recently e-mailed me on the subject. Ben references an October 2003 article published in the ASHRAE Journal, to which he contributed.

According to the article, written by Thomas H. Durkin and James B. (Burt) Rishel, “The advent of the small scroll or screw chiller, capable of producing condenser water as high as 140 degrees F. (60 degrees C.), created an opportunity for recovering heat from a dedicated heat recovery chiller’s condenser water circuit for heating or domestic water systems while providing beneficial cooling for the chilled water system. These systems are called ‘dedicated’ heat recovery because 100 percent of the heat generated by the DHRC can be used for hot-water heating applications. Also, the DHRC can be piped and controlled to produce the desired evaporator or condenser temperature. Transfer of the recovered heat in this article is limited to clean-water applications.

“The ability to recover heat from a chiller’s condenser has been improved due to the development of small-tonnage compressors that can operate at high-discharge pressures and be controlled from either the condenser or evaporator water temperatures. ... The heat-recovery chiller introduces an efficient answer to simultaneous heating and cooling loads. Three ways to accomplish this:

  1. Run boilers and chillers.
  2. Run boilers and operate air-side economizers.
  3. Run a heat-recovery chiller.

“Using a particular project’s energy rates, operating boilers and chillers cost $0.87 per 100 MBH (29.31 kW); boiler and economizers cost $0.59 per 100 MBH (29.31 kW), while the heat-recovery chiller required only $0.38 per 100 MBH (29.31 kW). This demonstrated that operating the DHRC required only 43.7 percent of that for running boilers and the chiller, and 64.4 percent for running boilers and air-side economizer simultaneously for that installation.”

Here’s what Ben has to say on the subject:

“... I think anyone advocating ‘green,’ environmentally or economically, must consider the benefits of DHRC. As much as it may appear to be ‘cutting-edge’ today, it should have been so in 1974!  It should be the predominant system used today.

“A hospital that has a large domestic water-heating load handled by gas or steam, and has a large cooling load at the same time, cannot consider itself ‘green’ if there is mechanical consumption of electrical energy to throw heat away at 1,000 Btu/lb, plus the energy needed to transfer and exhaust the heat ...

“It doesn't make a lot of sense to put a green building in a gray city. Before we consider ‘greening’ one building at a time, we should also realize that there are a lot of ‘heat plumes’ out there at this time of year that practically scream, ‘I'm blowing away heat at 1000 Btu/lb, and that doesn't include the energy to get the heat into the air!’

“If it is logical to install centralized (district) chilled-water plants for cities, it seems that it would be logical to distribute waste heat in the form of water, also. There's actually a lot of this energy that could be transferred as well. If a power plant that is now paying to condense steam to produce such impressive plumes would instead realize that energy is a commodity, they could pump the condenser water into town. Then, individuals could tap the heat via a heat pump, if required (areas next to foundries may not need a heat pump) using electrical power from the power company, which would reduce the gas consumption in winter and allow the power plant to operate at a more even year-round load.

“Plumes are fairly easy to pick out. They are actually there year-round. In summer, very little energy should be required for any hospital's domestic water loads.”

Referring once again to the ASHRAE Journal piece and to Ben’s earlier point, the authors conclude, “The application of heat-recovery chillers requires detailed evaluation of each installation. Success will be determined by the care provided for this evaluation. The use of heat-recovery chillers is an old procedure for energy conservation, but the development of digital control, along with special types of chillers and condensing boilers, is opening a new field of efficient chilled/hot water operations with the resultant energy conservation.”

This proves once again that an idea born before its time is still a good idea. It’s up to us as building professionals to strive to find suitable alternatives to the status quo, even if it means resurrecting an old idea. Or, as my friends (the Yoga Sutras of Patanjali) like to say, “When you are inspired by some great purpose, some extraordinary project, all your thoughts break their bounds. Your mind transcends limitations, your consciousness expands in every direction, and you find yourself in a new, great, and wonderful world.”


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